In recent years technology has been developed that gasifies organic solid material such as coal, biomass, and tire chips instead of oil in order to produce gasification gas. The gasification gas that is produced in this manner is used in efficient power generation systems known as Integrated coal Gasification Combined Cycle (IGCC) systems, and in the manufacturing of hydrogen, the manufacturing of synthetic fuel (i.e., synthetic oil), and in the manufacturing of chemical products such as chemical fertilizers (i.e., urea) and the like. Of the organic solid materials that form the raw materials for this gasification gas, the ratio of reserves to production (R/PR) for coal is approximately 150 years, which is approximately three or more times the R/PR of oil, and coal deposits are more evenly distributed compared to oil. Therefore, coal is particularly expected to be a natural resource that is capable of providing a stable supply for a considerable time into the future.
Conventionally, the process of gasifying coal is achieved by performing partial oxidation using oxygen and air, however, because an extremely high temperature of approximately 1800° C. and an extremely high pressure of approximately 3 MPa are required in this gasification process, special materials that are able to withstand high temperatures and high pressures are required so that the conventional technology has the drawback that the costs of the gasification furnace are extremely expensive. In order to solve this problem, technology has been developed that utilizes steam in order to gasify coal at comparatively low temperatures of between approximately 700° C. to 900° C., and at normal pressure. This technology has the advantages that, by setting the temperature and pressure at lower levels, special structure to withstand high pressure is not required, and commercially available items already in common use can be employed.
However, in the above-described organic solid material steam gasification reaction, a comparatively long reaction time is required. Accordingly, a fluidized bed is formed in the gasification furnace by supplying a fluidized medium such as sand that has been heated to a high temperature of, for example, 800° C. or more, and by supplying steam from underneath the gasification furnace. As a result, an adequate residence time for the organic solid material to react sufficiently is ensured. Gasification gas is then produced by injecting gasification raw material into the gasification furnace in which the fluidized bed has been formed, and performing fluidized heating on this gasification raw material.
In a gasification furnace in which a fluidized bed has been formed in this manner, of the sand and organic solid raw material that forms the fluidized medium, the solid particles having a small particle diameter separate from the fluidized bed together with the gasification gas and are scattered. In order to collect these scattered particles a gasification gas separator (i.e., a cyclone) that separates the gasification gas from the solid particles is installed in the discharge port of the gasification furnace. The solid particles collected by the gasification gas separator can then be returned to the gasification furnace (see, for example, Patent document 1).